Papers by Author: P. D'Hugues

Abstract: In the frame of a European project (BioMinE - FP6), a continuous bioleaching operation was carried out in a laboratory-scale unit using a cobaltiferous pyrite. The objective of the work was to use this system to investigate mechanisms of microbial activity and mineral oxidation in continuous stirred bioreactors (1x50L - 3x20L). A combination of scientific and technical approaches (molecular ecology, biochemistry and microscopy) was used and various key operating parameters were tested (temperature, nitrogen source, CO2 availability, designed consortia). An increase of temperature of 10°C (35°C to 45°C) had no major influence on the bioleaching efficiency. When the ammonium source was limiting, there was a negative influence on both bacterial growth and bioleaching efficiency. This result was related to a combination of factors such as less bacterial attachment to the pyrite surface and less precipitate formation. CO2 limitation had a very significant negative effect on the bacterial productivity and consequently on the bioleaching efficiency. Nevertheless, the population composition remained unchanged. An important decrease of EPS (sugar) production was also observed. The bacterial strains, that dominate the culture, originated from the deposit in Uganda. It seems that their bioleaching ability was improved over the time when cultured in continuous mode. The culture composition was very stable. The iron-oxidizer L. ferriphilum was the dominant organism in standard (not limiting) conditions, and was always very well represented during the first 3-4 days of residence time. Sulfobacillus sp. BRGM2 also played an important role in the process. This study gives new insights for the application of this technology, and more specifically on the influence of key operating parameters on bioleaching performances, population dynamics and attachment of bacteria to the solid surfaces.

Abstract: The Bioshale project, involving 13 partners throughout Europe, is co-funded by the European Commission under the FP6 program. The main objective of this project (which started in October 2004) is to identify and develop innovative biotechnological processes for ‘’eco-efficient’’ exploitation of metal-rich, black shale ores. Three extensive deposits have been selected for R&D actions. These are: (i) a site (in Talvivaara, Finland) that, at the outset of the project, had not been exploited; (ii) a deposit (in Lubin, Poland) that is currently being actively mined, and (iii) a third site (in Mansfeld, Germany) where the ore had been actively mined in the past, but which is no longer exploited. The black shale ores contain base (e.g. copper and nickel), precious (principally silver) and PGM metals, but also high contents of organic matter that potentially handicap metal recovery by conventional techniques. The main technical aspects of the work plan can be summarized as: (i) evaluation of the geological resources and selection of metal-bearing components; (ii) selection of biological consortia to be tested; (iii) assessment of bioprocessing routes, including hydrometallurgical processing; (iv) techno-economic evaluation of new processes from mining to metal recovery including social, and (v) assessing the environmental impacts of biotechnological compared to conventional processing of the ores. An overview of the main results obtained to date are presented, with special emphasis on the development of bioleaching technologies for metal recovery that can be applied to multielement concentrates and black shale ores.